I am an investigator in university conducting a research project about
muscle force regulation using surface mechanomyogram (MMG). The sensor I
used to detect "muscle sound" in the tibialis anterior was HP21050A.
However, HP will not produce HP21050A anymore, and the product is out of
stock. I also tried to contact other manufacturers that fabricate
piezoelectric sensors used in many published articles. Sadly, their
responses are not positive. To expedite the current project, other
piezoelectric accelerometer/microphone in place of HP21050A is required.
Your suggestion to solve this problem is highly appreciated.